Problems arise when mud flaps behind the rear wheels of trucks contact objects behind the truck as it is backing up. When this happens, the mud flaps are pinched against the rear wheels and are often torn away or otherwise damaged. Damaged mud flaps can disable a vehicle since federal law requires that all such trucks in interstate commerce include mud flaps in good condition and of sufficient length. Trucks traveling over the highway with damaged mud flaps are illegal and may be subject to fines and other penalties.
There have been suggested many different devices for moving or retracting dump truck mud flaps in order to cure the above-stated problem of damage caused to the mud flaps while backing up the truck. These devices are described, for example, in U.S. Pat. Nos. 2,653,846 to Wiley; 3,582,109 to Moore; 2,872,211 to Barrett; 3,640,577 to Ducote; 2,857,200 to Hoppesch; 2,721,760 to Lapham; 3,788,668 to Perger; 3,794,383 to France; 4,097,090 to Payne; and 5,582,431 to Anderson. These patents disclose various systems for moving the mud flaps away from the rear wheels, some of which are pneumatically operated. The various devices employ methods for either retracting each mud flap upward into an enclosure, moving it sideways, or pulling it up from above by a cable. The systems which retract mud flaps into an enclosure are very expensive and the mud flap can become jammed inside the enclosure by mud and other debris. The most economical of prior art mud flap protection systems are those employing cable operation, such as the system disclosed in U.S. Pat. No. 3,582,109 issued to Moore.
In the Moore system, a cable attached to the outside of each mud flap is pulled from above, folding the mud flap as it is lifted upward and rearward away from the truck tires. While this does not provide full retraction of the mud flap from behind the tires, the movement of the mud flap is sufficient to prevent damage without requiring a complex retraction system. However, the problem with cable-actuated systems such as disclosed by Moore is that the cables, because they are necessarily exposed and are located above and rearward of the mud flaps, can themselves become damaged by weather or contact with obstacles and loads at the rear of the truck. Furthermore, the attachment of the cables is often made directly to the mud flaps. This can cause cracking and damage to the mud flaps because the mud flap is weakened at the point of attachment since it is not designed to experience a pulling force at that point. Finally, cable systems such as the Moore system require that the mud flap be altered to receive the cable attachment, thereby increasing the cost of installation and making replacement of mud flaps more difficult and more costly. There is therefore a need in the art for an economical mud flap retraction system which prevents damage to mud flaps during normal operation of trucks, such as dump trucks, yet is economical and easy to use.